Method of treating gaseous media



Patented Aug. 4, 1936 2,049,t&

METHUD F TREATING GASEOWS HEB Pm Glenn C. Forrester, Niagara Falls, N. H.

No Drawing.

Application April 2'3, 19%,

Serial No. 7 ,22,633

8 Glaims.

absorption product possesses negligible vaporpressure, whereby absorption ofthe vapors from the gaseous system may be complete, not .reversible, and efiective for low as well as for high concentrations of vapors.

2. The absorbent should be of such a nature that the absorbed material can be recovered by a simple and inexpensive operation, unaltered chemically and with negligible loss.

3. The absorbent should be of low cost, and preferably also of the type which can be regenerated economically.

4. The absorption action should be rapid, i. e. recovery should be complete when treating a large volume of the gaseous carrier per unit of weight of absorbent perhour.

5. The weight of vapors absorbed per unit of weight of absorbent should be high;

4 6. The absorbent should be inert to the rest of the gaseous system.

7. The absorbent, both fresh and spent, should be capable of convenient handling and of suitable 0 form to permit rapid and intimate contact with a' gaseous system.

I have found that perchlorates, more particularly metallic perchlorates, and specifically magnesium perchlorate, possess characteristics which satisfy, to a practical extent, the characteristics desired for an ideal absorbent, as above mentioned.

It is, therefore, an object of this invention to provide a method of removing vapors of various volatile liquids or solids from a gaseous medium for the purpose of recovering said vapors or for purifying said gaseous medium by the use of a perchlorate or combination of perchlorates as an absorbent.

Another object of this invention is to provide an absorbent for vapors of volatile liquids or solids comprising a perchlorate or combination of perchlorates, whereby such vapors may be'removed from a gaseous medium containing the same for substantially the purposes set forth.

Other objects will become apparent from the following description and appended claims.

In accordance with the principles of the instant invention, a gaseous medium containing vapors of volatile liquids or solids, preferably after the removal of suspended foreign particles and moisture, is passed through or mixed with or otherwise brought in contact with an absorbent, hereafter more fully described, whereby the volatile vapors combine with or are absorbed by said absorbent and removed from said gaseous medium.

The absorption is continued until the vapor pressureof the absorbent and absorbed material approaches the partial pressure of the vapor to be absorbed in the gaseous medium. When the process is for the purpose of recovering the vaporized substances, the absorbent, together with the combined or absorbed material, is subjected to a process whereby the combined or absorbed material is separated from the absorbent and recovered. The absorbent is then subjected to a treatment whereby it is regenerated and then again utilized in the process. Alternatively, when the process is used for the purpose of purifying a gaseous medium, the absorbent, 'together with the absorbed material, may also be treated in the manner aforementioned for the purpose of regenerating the absorbent if the economics of the process warrant.

The preferred absorbent is one which does not deliquesce under ordinary conditions, yet has great absorption powers both with respect to quantity of substance held per unit weight of perchlorate, and firmness with which these substances are held; is easily regenerated without decomposition with a minimum of mechanical difficulties. Magnesium perchlorate is the specific preferred absorbent because it possesses the characteristics just enumerated.

I have found, however, that other metallic perchlorates, such as calcium, barium, strontium, zinc, cobalt, nickel, manganese, aluminum, etc., which normally contain water of crystallization and which can be successfully dehydrated without decomposition, may be used as absorbents. However, they are not as desirable as magnesium perchlorate for one or more of several reasons: namely, greater tendency to deliquesce; practical difficulties in dehydrating; low capacity to hold substances per unit weight of perchlorate; relatively higher vapor pressures exhibited by the combinations of these perchlorates and substances.

Anhydrous magnesium perchlorate absorbs moisture avidly. Thus, when anhydrous magnesiumperchlorate is exposed to the atmosphere,

it takes up moisture rapidly until it has gained approximately in weight, at which point further noticeable increase ceases at normal humidity. The resulting product corresponds to the formula Mgtcloi) 2.61-120, and the water is believed to be combined as water of crystallization. This increase in weight may be stopped at any varying indicated degrees of water absorptive capacity:

Rate of gas. Vapor eonfl It Absorbent plus percent centration Substance of substance in gm per per hr, per Absorption met lb. perchlorate - Percent Methyl alcohol 36% Mg(C104): N0l18 1216 3. 68 99. 6 Ethyl alcohol... 36% Mg(C104)2. 25% 1184 23. 36 100. G Isopropyl alcohol. 36% Mg(ClO4):.-. 33% 0647 41. 22 100. 0 Amyl alcohol 32% Mg(C1O4)g -30. 5%.. 0154 46. 37 100. 0 Butyl alcohol 36% Mg(ClO4)z- None 0108 39. 49 100. 0 Ethylene ehlorhydnn. 36% Mg(ClO4):..--None. 018 2.08 95. 9 Forrnic ae1d.. 36% Mg(Cl04)z None.- 054 2. 08 99. 2 Acetic acid- 36% Mg(ClO4) -..-.None 048 1. 85 99. 5 Ethyl acetat 46% MgClO4) -47. 2%.- 432 39. 84 92. 0 Butyl acetate- 36% Mg ClO4):..- None 0321 1. 3 97. 0 Ethyl lactate- 29.4% Mg(Cl04)1. Noue. 0193 2. 52 99. 1 Ethyl acetoacetate 30.1% Mg(C1O4)z- None.. 0093 3. 75 96. 5 Acetic enhydride-. 36% Mg C104)2..- N0i10.. 10228 1. 97 1 00. 0 Paralydehyde... 46% Mg Cl04)z None 157 36.06 100. 0 uriural 29.4% Mg(ClO4)g None 0116 2. 7 99. 0 Formaldehyde (30% 36% Mg(ClO4)a-. None. 0231 3. 26 81. 0 Acetone 36% Mg(OiO4)i -None-- 2. 45 99. 4 Methyl-etbylketone..- 36% Mg(ClO4)z. --None- .33 50. 3 100.0 Aceto-phenone 36% Mg(ClO4)z- None 00167 42. 36 100. 0 Diethyl amine... 36% Mg(ClO4)z. N0I16 5508 4. 8 96. 4 Allllllle 30.1% Mg(ClO4)z None .0043 3.36 96. a Monomethyl ether of diethylene glycol. 29.4% Mg(ClO4)z. None 0326 2. 97 90. 1 M onoethyl other of diethylene glycol. 30.1% Mg(ClO4)2 .None 0014 3. 43 93. 5 Diethyl ether 36% Mg(ClO4) None High Slow 84. 0 Benzyl-ethyl e 36% Mg(ClO4)z-- .38.4%.. 019 '6. 87 86. 0 1,4 d1oxane. 30.1% Mg(Ol04)z--None 1015 1. 56 73. 5

a compound having a predetermined amount of moisture. A salt substantially free of water. may be obtained by heating at 250 C. and'l mm. pressure. Also, this result can be secured by using lower temperatures and higher pressures than those named.'

To secure greatest absorptive capacity and greatest retentive power, magnesium perchlorate of maximum dehydration is preferably employed. However, even completely hydrated magnesium perchlorate shows significant absorptive powers for vapors of certain substances. I have found that for many purposes magnesium perchlorate, partially dehydrated, for example, one dehydrated to such a degree that it is capable of adding 36% of its weight of moisture, or one capable of adding 32%"of its weight of moisture, is satisfactory. Hereafter, the expressions 36% magnesium perchlorate and 32% magnesium perchlorate are .used to define magnesium perchlorate which isanhydrides, aldehydes, ketones, and amines, and,

to asmaller degree, ethers and phenols.

} The following table shows the indicated absorption of several illustrative substances when weighted quantities of said substances are vaporized and the air bearing the vapors is passed ,through weighted absorption tubes containing weighted quantities of magnesium perchlorate of One of the characteristic features of the absorbents contemplated by the instant invention is that the absorbent plus the absorbed substance possesses avery low vapor pressure, even when the weight of vapor absorbed per unit weight of absorbent is relatively high. As a consequence, substantially complete or nearly complete removal of the vapors of the volatile substances from'a gaseous medium, even when they are 'present in the gaseous media in such small amounts as to ex- 'hibit-very low partial pressures, and even after substantial amounts of the vapors have been absorbed, can be efiected.

To illustratejthe following table sets forth the already observed vapor pressures of definite amounts of magnesium perchlorate of varying indicated degrees of water absorptive capacity, plus definite amounts of volatile substances, and also the vapor pressure of the pure volatile substances, the vapor pressures being measured and calculated by a dynamic methodz' Vapor Vapor pres- Percent of substance pressure Percent w contained agas? of pure substance mm. mm. 19.7% Mggclodz..- 12.2% ethyl acetate... 08 106 10.7% Mg 0104):.-- 34.1% ethyl acetate...- 2.9 106 36% Mggclodzun- 35.7% ethyl acetate 05 106 36% Mg 0104):".-. 47.0% ethyl acetate. 58 46% g(Cl04)z. 38.2% ethyl acetate..- Negligible 106 46 Mg(Cl04). 47.2% ethyl acetate 02 106 46 o Mg(Cl04):. 42.2% ethyl acetate... .074 106 46 Mg(Cl04)1 58.8% ethyl acetate...- 81 106 46% M (0l0i)i.-.-l 36.0% butyl acetate- Negligible 12. 5 46% Mg(Cl04)1. 41.5% butyl acetate-.. .01 12. 5 46% Mg( 0104):" 56.9% butyl acetate 066 12. 5 46% Mg(ClO4); 33.2% butyl acetate.--. Negligible 12. 5 46% Mg(C-l04)z. 72.0% butyl acetate. .695 12.5 -32% Mg(Cl04)z....- 34.2% butyl acetate-.. I 033 12.5 32% Mg(ClO|)z 39.5% butyl acetate 113 12.5

32% Mg(OlO4)1.- 42.3% butyl alcohol..- 025 7. 5

32% Mg(ClO4)a. 41.4% acetophenone. Negligible 55 32% Mg(CIO4) 1...... 63.9% acetophenone. 004 55 32% Mg(Cl04). 36.41%, benzyl ethyl 49 7. 46 e or.

32% Mg(ClO|):.-. 57.4% benzyl eth'yl 57 7. 46

other.

36% Mg(GlO4):. 25.3% ethyl alcohol. Negligible 36% Mg(ClO4)z. 35.4% ethyl alcohol. Negligible Vapor Vapor Vapor pres Vapor pres- Percent of substance pressure Percent of substance rcssure Percent perchlorate contained z gg' of pure Percent perchlorate contained sure g' Bil pure substance Serve substance ,mm. mm. 36% Mg(ClO4);.-..- 33.2% lsopropyl alco- 24% Co(Cl04)1.. l3 5% ethyl acetate. .22 106 hol. 24% 00(0100: 16 6% ethyl acetate 43 106 36% Mg(Cl01):.. 49.7% lsopropyl alco- 24% Co(ClO4) 22.8% ethyl acetate .37 106 hol. 24% Co(Cl04) llztlllg lyacetatteh 1. 9.71 1% e .81 1 36% M c10l),. 35.9%paraldehyde- Clo time, y 36% Mg(Cl0|)1. 56.9% paraldehyde A( e mam-19.3% ethyl 4.34 106 3, ag g lglgnm gag 1, paralgegygen" gg ffig- 12 3g1: acetate.

g 4 para e y e-... 10.25.7 th l ace- 4.96 1 367:Mg(ClO4)z.-... 23.62% paraldehyde 3 tate. e y 06 m 5.9%4.1% ethyl ace- 1.36 106 36% Mg(ClO4)a.

methyl ethyl tate. a one. 23.47 Mn(Cl0 24.77 ethyl acetate.... .25 106 36% Mg(Cl04)z.--.. Mgfigflgnc y thyl 23. gngg ggau aosgjetg eeemtew 1 az 10s 23 n 16.7 at y acetate.... egigi e 106 3 a( l)=----- g e y ethyl eg igible 23.4% 10112211 3 lgetlhyllacetatcnn Negligible 10a 11 23.75 7 Ni 2e. at y acetate.... .40 106 Mrwl oa 640% yl e hyl 2.56 23.75%1; 0101);... 23.6%;ethylacetate. .095 10s ESl8 la-sa zrl ea a 5 i 4 e y aceta e 5 l):...-. 30.4% ace e .07 226 15.9% Ba 0104 flog-128.4% butyl al- 106 7.5

CO 0 322/ Mg(ClO4)z.-. 37.67 acetone .50 226 l 4 29, 327: Mg(ClO4)... 56.7%; acetic anhydride .63 15 9% Ba (Cloun' 337 5%e by} aw 14 9 106 32% Mgwlomhn 67.1%aceficacid 09 l5.9%Ba(Cl04)1. liil:t79.5% ethyl ace- 0.5 106 15.9% Ba (0104 las g loaz, butyl alv 2. as 7.5 00 O 11.17 butyl alcohol. Negligible 7.5 These data were obtained at 25 C. by a dy- 10.6%butylalcohoL." Negligible 7.5 namic method. The absorbent was contained in Ca(Cl04)l it deliig fjgm ifgmfi- U tubes and the substances were introduced into glm ggf ljf 16.6%ethyl acetate .45 lot the air intake arm of the tube. Because granule period over PZOI. & 1% size, physical structure, distribution of the subtate. 1 stances, and other factors influence moderately the results obtained, these data and other data disclosed in this application are subject to some small discrepancies. However, they represent faithfully the order of magnitude to be obtained in similarly conducted experiments.

The following table shows the indicated absorption of several other illustrative substances when weighed quantities of said substances 'are vaporized and the air bearing the vapors is passed through weighed absorption tubes containing weighed quantities of the named perchlorates,

which, in most instances, are already combined with the indicated quantities of substances:

Another characteristic feature of the absorbents contemplated by the instant invention is that absorption of the vapors is rapid at the same time that it is complete or nearly complete; and even after the absorbents have taken up a considerable quantity of vapors, the percentage of vapors absorbed is still high, which means that these partially spent absorbents can still be used in stripping the gaseous media of part of their vapor content. sage of large volumes of the gaseous media Gals strearrtn ra cu.

Percent perchlorate Percent ggggf con ggf 'gggz g sub criminal. per lb. of

perchlorate per hour 25.0% ethyl acetate; 83.7% ethyl acetate .42 4. 46 24.0% ethyl acetate. 76 3% ethyl acetate 414 41. 2 13.0% ethyl acetate- 94 8% ethyl acetate. 414 41. 2 19.0% ethy acetate. 6% ethyl acetate 0167 2 15 25.0% ethyl acetate.. 30 0% ethyl acetate. 369 39. 8 12.0% ethyl acetate" 98 0% ethyl acetate" 369 19. 9 15.2% ethyl acetate.. 84 0% ethyl acetate 0114 33. 3 26.2 ethyl acetate 64 0% ethyl acetate 3868 68. 7 6.5% ethyl acetate... 56 0% ethyl acetate 1386 68. 7 27.1 ethyl acetate 73.5% ethyl acetate 3700 39.8 13.6% ethyl acetate 97.9% ethyl acetate 3700 10. 9 16.6% ethyl acetate 63 7% ethyl acetate 010 3. 77 22.6% ethyl acetate- 68 0% ethyl acetate 38 3. 0

0.0% hutyl alcohol. 53.0% butyl alcohol 02 7. 7 16.5% butyl alcoh 2% butyl alcohol 02 10. 7 30 4% butyl alcohol 92 8% butyl alcohol 02 57. 6 71.6% butyl alcohol 88 9% butyl alcohol 023 23. 7 101.0% butyl alcohol 88.0% butyl alcohol. 02 30. 2

The following table sets forth the observer vapor pressure of the named absorbent plus a definite amount of volatile substancez.

through not unduly large quantities of absorbent and obviates the necessity of unduly bulky absorption chambers.

These characteristics permit pas- The following table sets forth some of the results observed in the absorption of vapors by the contemplated absorbents held in U tubes:

der reduced pressure, whereby the absorbed material is permitted to pass off as a vapor. This process, with alcohols and some other high boil- GtSS strea}? Percent of substance con- Percent of vapors of sub- Grams per m a: percentperchlorate tained stance absorbed liter per perchlorate per hour 19.7% Mg(Cl0l)= 34.6% ethyl acetate 57.0% ethyl acetate .403 16. 5 19.7% Mg 34.1% ethyl acetate.. 76.0% ethyl acetate. 458 3. 4 32.0% M 46.5% ethyl acetate. 84.0% ethyl acetate. 4 3. 0 32.0% M 58.1% ethyl acetate. 67.5% ethyl acetate 4 3. 0 32.0% Mg( 35.2% ethyl acetate.- 73.0% ethyl acetate.- 015 9. 2 46.0% Mg( 47.2% ethyl acetate.. 92.0% ethyl acetate.. 432 40. 0 46.0% M 50.5% ethyl acetate.- 72 5% ethyl acetate- 427 67. 0 46.0% M 54.7% ethyl acetate.. 68.0% ethyl acetate.. 017 2 3 46.0% M 42.2% ethyl acetate.- 86 0% ethyl acetate.. 018 16. 0 32.0% M 03.0% ethyl acetate.. 0093 5. 75 32.0% M 96.4% ethyl acetate 4 3.0 40.0% Mg( 94.5% butyl acetate .061 61.0 46.0% Mg 96.0% butyl acetate. 057 3.79 32.0% Mg(ClOl)1. 95.0% butyl acetate. 0655 16. 0 82.0% Mg(C 79 0% butyl acetate. 064 85. 0 32.0% Mg(ClOl) 87.0% butyl acetate. 054 4. 1 32.0% Mg(ClO4) 48.6% butyl acetate 79.0% butyl acetate 048 1. 7 32.0% Mg(ClO4)2 54.9% butyl alcohol 93.9% butyl alcohol 015 38.0 32.0% Mg(ClO4);- 56.3% butyl alcohoL. 87.1% butyl alcohol .023 76.0 32.0% Mg(Cl)l 56.7% butyl alcohol 100.0% butyl alcohol-.'. 010,3 5. 0

32.0% Mg(ClO4)2 50.9% acetic anliydrida. 93.4% acetic anhydride... N681; satu- 3. 0

, ra lon 32.0% Mg(ClO4)2.--.--.. 52.5% acetic acid 90.1% acetic acid Near satua 0 ration 32.0% Mg(ClO4)z 32.1% acetone 97.7% acetone... Neaisatu- 3. 0

ra lcn 32.0% Mg( C1002 63.9% acetophenone... 94.0% acetophenone.. 0017 42. 5 32.0% Mg(ClOl)z 04.3% acetophenone. 84.0% acetophenone.- 002 111. 0

32.0% Mg(ClOi)z 57.0% benzyl ethyl ether-. 85.0% bcnzyl ethyl ether.. 019 34.5 32.0% Mg(Cl0.,) 60.5% benzyl ethyl ether.. 75.0% benzyl ethyl. ether-. 0126 75. 9

36.0% Mg(C-1O4)z 30.l% ethyl alcohol 90.5% ethyl alcohol 1184 23. 4 36.0% Mg(ClOl)2.. 53.4% ethyl alcohoL.. 59.3% ethyl alcohol.. 097 44. 0 36.0% Mg(C1O )z 26.5% ethyl alcohol--. 92.0% ethyl alcohol 023 1. 45

32. Mg(Cl0i)2 44.6%amyl alcohol. 00.2% 8.1113! alcohol .0154 46. 0 32.0% Mg(ClO4)z 64.5% amyl alcohol- 80.8% amyl alcohol 018 39. 0

36.0, g(ClO4)l 51.3% isopropyl alcohol. 90.3% isopropyl alcohol. 1316 45. 0 36.0% Mg(Cl04)z 76.2% isopropyl alcohol. 85.0% isopropyl alcohol-.- 133 2. 6 36.0% Mg(Ol0l) 44.5% paraldehyde..-....- 67.0% paraldehyde 138 0 46.0% Mg(ClO4) 0.0% paraldehyde 100.0% paraldehyde 138 3.0 30 0% Mg(C104): 321% methyl ethyl e- 0e 0% methyl ethyl ke- .33 50.0

- one. one. 30.0% Mg(O10l): 52. 0% methyl ethyl ke- 43i0% methyl ethyl ke- 402 65.0

. one. one. 360% Mg(ClO4)z-. 54.2% methyl ethyl ke- 890% methyl ethyl ke- 300 2. 8

tone. one.

It is here explained that the results hereinbefore set forth were carried out on a laboratory scale at a temperature of approximately C. to approximately 30 C., unless otherwise indicated.

Recovery of the substances absorbed ,as hereinbefore set forth can be secured by a simple and inexpensive process. The absorbed vapors appear to function somewhat as does water of crystallization. In most instances, as the content of the vapor absorbed increases, the perchlorate salt dissolves in the solvent of crystallization to form a viscous fluid which becomes less viscous as it becomes more diluted by additional vapors absorbed. As this stage is reached, the vapor pressure increases perceptibly, and, in the vapor ab-' vapor pressure of the absorbent plusthe absorbed substance approaches the partial pressure of the substance in the gas stream, the absorbent and.

the absorbed substance are removed and subjected'to a. process whereby recovery of the absorbed material is made possible. .The recovery of these substances may be effected by heating the salt containing the absorbed substance slowly uning substances, appears to decompose some of the substance absorbed, and the dried perchloate residue is discolored with carbonaceous material. In this state, the perchloate does not absorb water or other vapors as efliciently as. before. The original efilciency can be secured by dissolving the discolored salt in water, filtering, evaporation, and suitable dehydration.

' Preferably, the perchlorate plus the absorbed substance can be treated with a small quantity of water to efiect complete solution of the salt. When the absorbed substance is one which is not miscible with water, the mixture may be allowed to settle and the substance separated by decantation. The separation in this case may also 'be secured by fractional distillation. The solution containing the absorbent is evaporated, preferably after filtering, and after dehydration the residue can be re-used in the absorption process. 1

The apparatus for carrying out the process is simple. The perchlorate, either in solid granular passed therethrouzh. Inasmuch as the perchlothe perchlorate.

rates have a marked tendency to combine with water and thereby lose proportionally the ability to absorb and retain vapors of other substances, I prefer, if the gaseous medium contains any moisture, to remove said moisture in any con-' venient manner which does not afiect the vapors to be absorbed, prior to bringing said medium in contact with the perchlorate. Likewise, I also prefer to remove any suspended solids from the gaseous medium prior to contacting with The period of contact between the gaseous medium and the absorbent is adjusted so that substantially complete removal of the desired vapors is secured. It is, ofcourse, to be understood that a plurality of absorbent chambers may be provided. When a plurality of vapors are simultaneously absorbed, they may be separated from the absorbent either singlyor together. In the latter case, the'mixt ure of the 'two substances may be separated in any suitable manner, such as fractional distillation, extraction, etc.

Since it is obvious that various changes and modifications may be made in'the above description without departing from the nature or spirit thereof, this invention is not restricted thereto except'as set forth in the appended claims.

, I claim:

1. A method of removing vapors of volatile organic. substances, such as alcohols, acids, esters, anhydrides, ketones, amines, aldehydes, etc., from a gaseous medium which comprises causing said gaseous medium to contact with a metallic perchlorate.

2. A method of removing vapors of volatile organic substances, suchas alcohols, acids, esters, anhydrides, ketones, amines, aldehydes, etc:, from a gaseous medium which comprises causing said gaseous medium to contact with magnesium perchlorate.

40 3. A method of removing vapors of volatile orv of its weight of moisture.

5. A method of recovering vapors of volatile organic substances, such as alcohols, acids, esters, anhydrides, ketones, amines, aldehydes, etc., from.

a gaseous medium which comprises causing said gaseous medium to contact with a metallic perchlorate, removing the absorbed compound from the said perchlorate, andreusing the perchloratein the process.

6. A method of recovering vapors of volatile J org'anicrsubstances, such as alcohols, acids, esters,

anhydrides, ketones, amines, aldehydes,. etc., from a gaseous medium which comprises causing said 25' I gaseous medium to contact with magnesium perchlorate containing from approximately 0 to approximately 50% moisture, removing the absorbed compound from the said perchlorate, and

reusing the perchlorate in the process.

'7. A composition for absorbing vapors of vola-. tile organic substances, such as alcohols, acids, esters, anhydrides, ketones, amines, aldehydes, etc., comprising a metallic perchlorate.

8. A composition for absorbing vapors of volatile organic. substances, such as alcohols, acids, esters, anhydrides, ketones, amines, aldehydes, etc., comprising ma esium perchlorate containing approximately 0 to approximately 50% moisture.

- GLENN C. FORRESTER. 

